Fire Detection (1 of 5)
Its strong sensitivity to sub-pixel "hot-areas" makes the 3.9 um channel very
useful in fire detection. Fig. 5a may be used to
compare the temperatures at 3.9 and 10.7 um with the percent of a pixel
covered by fire, where the hot-area is at 500 K and the remainder of the pixel
is at 300 K. Note that if only 5% of the pixel is at 500 K, the 3.9 um measured
brightness temperature of that pixel is 360 K, while the corresponding 10.7 um
brightness temperature is less than 320 K.
Fig. 5b shows the DIFFERENCE in the brightness temperature for the 3.9 and
10.7 um pixel, hypothesized in this example. Note how much more responsive
the 3.9 um channel is over smaller fire areas.
NOTE: Refer to the text with Fig. 2c, in the "Energy Sources" section, for an
important caveat regarding 3.9 um channel saturation.
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